* In formal exchange between banks, the peso fell 0.34 percent to 3.715/3.7175 per dollar ARS=RASL.

* In informal trade between foreign exchange houses as measured by Reuters, the peso retreated 0.13 percent to end at 3.74/3.745 ARSB=. (Reporting by Walter Bianchi and Jorge Otaola; Writing by Kevin Gray; Editing by Dan Grebler)